1. Field of the Invention
The present invention relates to susceptors for heat treating or cooling a substrate, and more particularly, to a susceptor used in a substrate heat treatment device that heat treats or cools substrates such as semiconductor wafers and LCD glass as part of the manufacturing process of semiconductor elements and LCD panels.
2. Description of the Related Art
In the manufacturing process of semiconductor elements and LCD panels, heat treatment and cooling of a substrate [31] such as a semiconductor wafer or LCD glass is carried out using a substrate heat treatment device [30] like that shown in FIG. 33. In this substrate heat treatment device [30], a susceptor [32] that heats or cools the substrate [31] is structured such that a heat source or cooling source [33] is conjunctively inserted between a heat transfer plate [34] and a retainer plate [35]. Materials having outstanding thermal conductivity, such as aluminum, aluminum alloys, copper and copper alloys, are used as materials for the heat transfer plate [34] and the retainer plate [35]. The heat transfer plate [34] and the retainer plate [35] are conjoined by welding or soldering the outer peripheries thereof. However, because pinholes or enclosed gas are generated at this time, there is the problem that the strength of the conjoined portion is decreased. Furthermore, when the interior of the substrate heat treatment device [30] is made to be a vacuum, there is the problem that gas leaks from the pinholes, thus lowering the vacuum level and exerting a deleterious effect on the heat treatment of the substrate [31].
In order to resolve these problems, Patent Literature 1 proposes a susceptor in which a protruding ring part and a groove part are provided facing each other on the joining surfaces of the heat transfer plate and the retainer plate. These parts are then combined and joined by press forging.
However, because the protruding ring part and the groove part are simple in shape, there is the problem that it is difficult to improve the airtightness of the susceptor to the degree that would allow heat treatment in a high vacuum or in a liquid. There is also the additional problem that because press forging is conducted by raising the temperature to near that of the temperature of the heating area used as the heater plate (for example, 400° C.), there is the likelihood that the materials of the heat transfer plate and the retainer plate will deform, thereby causing the structure and the characteristics of the susceptor to change. Such change additionally requires special equipment and operations, resulting in higher manufacturing costs.    Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2002-270347